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The use of commercial finite element analysis (FEA) software to perform stamping feasibility studies of automotive components has grown extensively over the last decade. Although product and process engineers have now come to rely heavily on results from FEA simulation for manufacturability of components, the prediction of springback has still not been perfected. Springback prediction for simple geometries is found to be quite accurate while springback prediction in complex components fails to compare with experimental results. Since most forming simulation FEA software uses a dynamic explicit solution method, the choice of various input parameters greatly affects the prediction of post formed stresses in the final component. Accurate stress prediction is critical for determination of springback, therefore this study focuses on the effects of some of the simulation parameters such as, element size, tool/loading speed and loading profile.

Two active boom noise damping techniques using a Helmholtz resonator-based compensator and a lead compensator called a positive pressure feedback have been developed at the University of Dayton [1]. The two damping techniques are of feedback type and their compensators can be implemented in software or hardware (using inexpensive operational amplifiers). The active damping system would rely on a speaker, a low-cost microphone, two accelerometers, and an electronic circuit (or a micro-controller) to add damping to the offending low-frequency vibroacoustic modes of the cavity. The simplicity of the active boom noise damping system lends itself to be incorporated into a vehicle's sound system. The Helmholtz resonator-based strategy is implemented on a Dodge Durango sport utility vehicle. The control scheme adds appreciable amount of damping to the first cavity mode and the first structurally induced acoustic mode of the cabin.

One of the key elements in efforts to minimize the noise emmissionis of engines and other machinery is the knowledge of the main noise radiating surfaces and the relation between measurable surface vibration and the sound pressure. Under the name of Airborne Source Quantification (ASQ), various techniques have been developed to discretize and quantify the source strength, and noise contributions, of vibrating surface patches of machinery or vehicle components. The noise contributions of patches to the sound pressure at specific locations in the sound field or to the total radiated sound power are identified. The source strength of equivalent point sources, the acoustic transfer from the source surface to critical sound field locations and finally the sound pressure contributions of the individual patches are quantified. These techniques are not unique to engine application, but very relevant for engine development. An example is shown for an engine under artificial excitation.

This paper describes the use of Vibro-Acoustics numerical modeling for prediction of an Air Intake System noise level for a commercial vehicle. The use of numerical methods to predict vehicle interior noise levels as well as sound radiated from components is gaining acceptance in the automotive industry [1]. The products of most industries can benefit from improved acoustic design. On the other hand, sound emission regulation has become more and more rigorous and customers expect quieter products. The aim of this work it is to assess the Vibro-Acoustics behavior of Air Intake System and influence of it in the sound pressure level of the vehicle.

The need for low pass filters stems from a need to eliminate high frequency noise from raw data (the output of the data acquisition system). As an example, consider the frame of a vehicle used in a crash test. The frame will exhibit high frequency vibrations, which do not affect the vehicles movement in space. The use of filters has since been expanded to include such things as the calculation of potential injury. Phaseless filters are now required for all FMVSS-208 injury calculations (see references). A single filter formula can not allow all test facilities to comply with the J211 CFC corridors. Even the SAE J211 recommended Butterworth filter may not comply with the J211 requirements. A new, universal, filtering system is required to harmonize the data processing at all testing facilities. The use of Fourier series for filtering provides a very powerful, yet overlooked, solution to today's filtering problems.

This paper show how the automotive product development process is presented in four distinct stages. The specific type of task, to be presented at each stage, is discussed. Specific CAE (Computer-Aided-Engineering) tasks, such as FEA (Finite Element Analysis), to be used at each stage are discussed. Detailed steps to follow are presented, as well as a check list of tasks are included. The changes and increased effectiveness (developed over 15 years of utilization) are discussed.

In this paper, the effects of roller geometry on contact pressure and residual stress in crankshaft fillet rolling are investigated by a two-dimensional finite element analysis. The fillet rolling process is first introduced to review some characteristics of the rolling tools. A two-dimensional plane strain finite element analysis is then employed to qualitatively investigate the influence of the roller geometry. Computations have been conducted for eight different contact geometries between the primary roller and the secondary roller to investigate the geometry effect on the contact pressure distribution on the edge of the primary roller. Fatigue parameters of the primary rollers are also estimated based on the Findley fatigue theory. Then, computations have been conducted for three different contact geometries between the primary roller and the crankshaft fillet to investigate the geometry effect on the residual stress distribution near the crankshaft fillet.

As the volume and complexity of electronics increases in automobiles, so does the complexity of the electromagnetic relationship between systems. The reliability and functionality of electronic systems in automobiles can be affected by noise sources such as direct current (DC) motors. A typical automobile has 25 to 100+ DC motors performing different tasks. This paper investigates the noise environment due to DC motors found in automobiles and the requirements that automobile manufacturers impose to suppress RF electromagnetic noise and conducted transients.

Power train noise reaches the interior through structureborne paths and through airborne transmission of engine casing noise. To determine transfer functions from vibration to interior noise a shaker was attached at the engine attachment points, with the engine removed. A simple engine noise simulator, with loudspeaker cones on its faces, was placed in the engine compartment to measure airborne transfer functions to interior noise. Empirical noise estimates, based on the incoherent sum of contributions for individual source terms times the appropriate transfer function, compared remarkably well with measured levels obtained from dynomometer tests. Airborne transmission dominates above 1.5kHz. At lower frequencies engine casing radiation and vibration contributions are comparable.

The cambore distortion is one of major concerns of an engine performance. A good design does not ensure a quality product. To meet product performance requirements, engineering community turns efforts to both design and manufacturing at an early stage of product development. This paper will discuss this process by providing an example of design and manufacturing of an overhead cambore. In this study a methodology to evaluate bore distortions is introduced. FEA cambore distortion analysis will use it to provide necessary data so that the product team can make a sound decision.

The vibration-generating mechanisms inside an engine are highly non-linear (combustion, valve operation, hydraulic bearing behavior, etc.). However, the engine structure, under the influence of these vibration-generating mechanisms, responds in a highly linear way. For the development and optimization of the engine structure for noise and vibration it is beneficial to use fast and ‘simple’ linear models, like linear FE-models, measured modal models or measured FRF-models. All these models allow a qualitative assessment of variants without excitation information. But, for true optimization, internal excitation spectra are needed in order to avoid that effort is spent to optimize non-critical system properties. Unfortunately, these internal excitation spectra are difficult to measure. Direct measurement of combustion pressure is still feasible, but crank-bearing forces, piston guidance forces etc. can only be identified indirectly.

Single-plane balancing is a very well-understood process, whereby an imbalance vector is determined and then opposed by a similar vector of equal magnitude but 180° out of phase. This is used in many situations to improve machine performance, vibration, noise etc. However, there is inherent in this process a sensitivity to errors of measurement and correction, since a large imbalance vector and the equally large correction vector must be of exactly equal magnitude and exactly 180° apart for perfect balance. This paper examines the effect of errors in measurement of the initial imbalance and correction of it on the residual balance of automotive drivelines. In particular, it examines the effects of the errors present in a system whereby a system balance correction is made, on a driveline assembly, at discrete points around a given plane (at bolt locations). Errors occur in measurement of vibration, in calculating correction masses and in applying those correction masses.

In this paper, the fatigue failure of the primary roller used in a crankshaft fillet rolling process is investigated by a failure analysis and a two-dimensional finite element analysis. The fillet rolling process is first discussed to introduce the important parameters that influence the fatigue life of the primary roller. The cross sections of failed primary rollers are then examined by an optical microscope and a Scanning Electron Microscope (SEM) to understand the microscopic characteristics of the fatigue failure process. A two-dimensional plane strain finite element analysis is employed to qualitatively investigate the influences of the contact geometry on the contact pressure distribution and the Mises stress distribution near the contact area. Fatigue parameters of the primary rollers are then estimated based on the Findley fatigue theory.

With the increased application of high strength steels in automotive body-in-white parts for weight reduction purposes, more emphasis is focused on springback as a major problem in stamping operations, in addition to panel breakage and wrinkling. Computer simulations using the finite element analysis (FEA) have been used to predict springback during early stages of die development processes to minimize potential springback related problems in production. However, the reliability of the springback simulation results relies directly on the accuracy of stress distributions from the forming simulation. Its complexity has brought many challenges not only to engineers and researchers in areas of FEA development and material modeling but also to FEA code end users. It is shown from this study that the springback simulation results vary with the yield criterion used in the forming simulation.

Barrier impacts are routinely used to estimate the impact response of vehicles in vehicle-to-vehicle crashes. One area of investigation is the detection of the secondary energy absorbing structures provided for under-/over-ride mitigation as a result of increased structural engagement -- improved geometric compatibility. The flat rigid barrier and the Transportation Research Laboratory’s (TRL) full width honeycomb barrier are commonly considered. In the present study, a vehicle-to-vehicle impact that exhibited no under-/over-ride condition was compared to finite element analysis of vehicle impacts to the two different barriers in order to evaluate their ability to detect the secondary energy absorbing structure. This study demonstrates that the rigid barrier and the TRL barrier yield similar quantitative information with regard to vehicle-to-vehicle crashes.

This paper presents the results of optimization study for sunroof buffeting reduction using CFD technology. For an early prototype vehicle as a baseline model in this study a high level of sunroof buffeting 133dB has been found. The CFD simulation shows that the buffeting noise can be reduced by installing a wind deflector at its optimal angle 40 degrees from the upward vertical line. Further optimization study demonstrates that the buffeting peak SPL can be reduced to 97dB if the sunroof glass moves to its optimal position, 50% of the total length of the sunroof from the front edge. For any other vehicles, the optimization procedure is the same to get the optimal parameters. On the other hand, however, this optimization study is only based on fluid dynamics principle without considering manufacturability, styling, cost, etc. Further work is needed to utilize the results in the production design.

The performance of shunt piezo damping is demonstrated by adding damping to the first mode of a plate with the dimensions of 28 by 38 cm and thickness of 0.8 mm. A small 1 by 2 inch piezoelectric patch with the thickness of 10 mil is bonded to the plate at a location where strain due to the first mode of vibration is high. The peizo is shunted with a resistance-inductance (RL) circuit, tuned to the first resonance frequency of the plate at 38 Hz. The plate is excited at its first natural frequency and the power spectrums of the acceleration at the center of the plate with and without the damping treatment were measured. These measurements showed that the shunt piezo damping treatment tuned to the first mode added an appreciable amount of damping to that mode.

This paper presents the results of CFD study on sunroof buffeting suppression using a dividing bar. The role of a dividing bar in side window buffeting case was illustrated in a previous study [8]. For the baseline model of the selected vehicle in this study, a very high level of sunroof buffeting, 133dB, has been found. The CFD simulation shows that the buffeting noise can be significantly reduced if a dividing bar is installed at the sunroof. A further optimization study on the dividing bar demonstrates that the peak buffeting level can be reduced to 123dB for the selected vehicle if the dividing bar is installed at its optimal location, 65% of the total length from the front edge of the sunroof. The peak buffeting level can be further reduced to 100dB if the dividing bar takes its optimal width 80mm, 15% of the total length of the sunroof for this vehicle, while staying at its optimal location.

NVH engineers typically are dealing with issues that relate to shake, harshness and low frequency noise and vibration concerns. However there is a greater importance being placed on dealing with high frequency structureborne noise problems which are related to gear meshing forces and drivetrain dynamics. This paper presents a case study of a high frequency structureborne noise problem. The objective of the paper is to show the application and effectiveness of using various testing based techniques such as Transfer Path, Running modes, and Mobility analysis along with acoustic excited operating deflection shapes for solving these problems in a timely and effective manner.

During the development of a Statistical Energy Analysis (SEA) model, the most important step leading toward higher quality and confidence is the model validation process. In this paper, three different ideal source environments are employed to validate a SEA model of a minivan; diffuse field in a reverberation room, free field in an hemi-anechoic room and single-point excitation by a shaker. The tests were intended to emphasize the air-and structure-borne paths of the model separately. During the reverberation room test, capability of the model to track the design changes was checked by perturbing the configuration of the vehicle in successive steps. Finally, the performance of the validated SEA model is demonstrated by using an operational load case.